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>> In this episode, we looked at the Physics issues that make ramps so useful.
Ramps are simple machines that allow you to use gentle forces to lift and lower
heavy loads. You exert those forces uphill as the, as
the heavy loads move long distances along the ramp.
The story of ramps is also the story of energy and work.
It's the story of energy because energy is a conserved quantity that depends only on
the situation. So that, in this case, the wagon has a
certain amount of energy. And now, it has more energy, the energy
increase in going from here to here, is all in the form of gravitational potential
energy, the energy stored in the force of gravity.
The story of ramps is also a story of work because in going from this position to
this position, you have to do a certain amount of work on the wagon to increase
its gravitational potential energy from its low value to its high value.
You're responsible for that increase in energy and you can do that, the work
necessary to increase the wagon's energy, either by lifting it straight up with a
large force exerted as it moves, as the wagon moves a small distance, or with a
gentle force as the wagon moves a long distance.
So, the work you do via either of these two approaches is and has to be the same
because the wagon's increasing energy is the same.
In addition to looking at energy and work in this episode, we also looked at a new
force, support forces. Support forces appear whenever two
surfaces try to occupy the same space at the same time.
And those support forces are exerted perpendicular to the surfaces involved.
For example, when the surface involved is horizontal as the end of the sidewalk, the
support forces that, that a horizontal surface exerts are vertical, as indicated
by this stick. But if the surface that you're looking for
looking to, to obtain support forces from, is tilted as it is with our ramp, the
support forces are no longer vertical. They are still perpendicaular to the
surface, but that's no longer straight up and down.
That pp and, in this case, to the right support force from a ramp, from this ramp
cannot cancel, in this case, the wagon's downward weight.
There is a residual left. When the two forces act on the wagon, the
residual that is left is the downhill ramp force.
And that ramp force, left unchecked, will cause the wagon to accelerate downhill.
We also talked about the third of Newton's Laws, Newton's Third Law of Motion, which
observes that for every force that one object exerts on a second object, the
second object exerts a force back on the first object that is exactly equal to the
amount and exactly the opposite direction. If my, what you see, this hand pushes on
this hand, this hand pushes back on this hand equally hard in the opposite
direction every time. It does not depend on whether the hands
are accelerating or moving in any way they like.
Newton's Third Law works. That's it for ramps.
Do your homework, study hard, and I'll see you next time, as we continue to look at
how things work.